Why did I get breast cancer if genetic tests were negative?

Question

Hello doctor,

This is more of a genetics-related question than a cancer treatment question. I am a 43-year-old woman who was recently diagnosed with breast cancer. What makes my situation particularly confusing is that several relatives in my family have undergone hereditary cancer genetic testing over the years, and we were told that all of their results were negative.

Because of that, I assumed our family's inherited cancer risk was relatively low. My diagnosis has left me wondering how breast cancer could develop at age 43 despite a family history of negative genetic testing.

Do current hereditary cancer tests miss certain mutations or genetic factors that have not yet been identified?
Is it possible that there are inherited risks that existing testing cannot detect?
Alternatively, do non-genetic factors sometimes play a larger role in the development of breast cancer than many people realize?

I would appreciate some insight into how a person can develop breast cancer at a relatively young age, even when hereditary cancer testing in the family has reportedly been negative.

Please help.

Thank you.

Answer 1

Hello,

Welcome to icliniq.com.

I have read your query.

I can understand why this would feel confusing, especially when multiple family members have previously undergone hereditary cancer testing and were told that no concerning mutations were found. However, a negative genetic test in your family does not completely eliminate the possibility of inherited cancer risk.

Breast cancer can develop through a complex interaction of genetic, hormonal, environmental, and lifestyle factors. While certain inherited mutations, such as those associated with hereditary breast cancer syndromes, can significantly increase risk, they account for only a portion of all breast cancer cases. Many people who develop breast cancer do not have an identifiable mutation on currently available genetic tests.

It is also important to consider that genetic testing has evolved considerably over time. Some relatives may have undergone older testing that examined only a limited number of genes, whereas newer panels can evaluate a much broader range of cancer-associated genes.

Even with modern testing, however, there are likely inherited risk factors that science has not yet fully identified, and some families may have an increased cancer susceptibility due to the combined effect of multiple small genetic variations that standard testing does not detect.

For these reasons, a diagnosis of breast cancer at age 43 does not necessarily mean that your relatives' previous genetic test results were incorrect. Rather, it highlights the fact that a negative hereditary cancer test does not rule out every possible inherited risk.

Given your diagnosis, it would be reasonable to meet with a genetic counselor or cancer genetics specialist. They can review your personal and family history, assess the type and timing of any previous testing performed on your relatives, and determine whether updated or expanded genetic testing may provide additional information for you and your family.

I hope this answers your query.

Please let me know if I can assist you further.

Thank you.